Half-duplex alternating-current telegraph system



R. D. PARKER.

HALF DUPLEX ALTERNATING CURRENT TELEGRAPH SYSTEM.

APPLICATION FILED SEPT-8. I919.

Patented Sept. 20,1921.

INVENTOR. fiflfimer lllllllllll A TTORNEY UNITED STATES PATENT OFFICE.-

narlznmonn n. manna, or BROOKLYN, new YORK, ASSIGNOR 'ro AMERICANmamrnoun AND TELEGRAPH COMPANY, A CORPORATION or NEW YORK.

nALr-nurnnx AL'rnnimrmo-cunmr TELEGRAPH srsrmr.

To all whom it my concern:

Be it known that I, 'RALZEMOND D. PARKER, residing at Brooklyn, in thecounty of Kings and State of New York, have invented cer- 5.tain Imrovements in Half-Duplex Alternatingurrent Telegraph Systems, of whichthe following is a specification.

This inventionrelates to signaling circuits and more particularly totelephone lines composited for Morse or other telegraph operation, andprovided with arrangement for superposing carrier current signalingchannels thereon.

One of the principal features of this invention resides in the provisionof an alternating current signaling channel for. a

transmission line, so arranged as to be operated upon a half duplexbasis by means of standard telegraph equipment such as is 'now used fortransmitting Morse signals.

Other and further features of the invention will be more'fullyunderstood from the following description when read in connectionwith the accompanying drawing, the

figure of which illustrates a circuit diagram embodying one form of theinvention:

In the diagram ML designates a telephone transmission line rovided withcomposite apparatus CX at its terminal station, for

superposing Morse signals upon the line.

The composite apparatus is of the usual and -we ll-lmown form and neednot be described herein. In order to provide an alternating carriercurrent signaling channel, a tuned branch TBis bri ged across themainline ML, said tuned branchhaving associated therewith a carriercircuit, CC, coupled thereto through the transformer 1. Included in saidcarrier circuit CC are the four windings 10, 11, 12 and 13,,gof adifferential alternating current receiving relay DR. A transmittingcircuit TC is bridged across the midpoints of the-windings of thedifferential relay DR, so that-by the provision of a balancingartificial line or network MN energy from the transmitting circuit TCwill not efiect the receiving-relay DR. The transmitting circuit T'Cincludes an alternating current generator G and a contact controlled by.the armature of the relayPR, which may be the standard pole changingrelay employed in half duplex Morse systems. As is well understood, thispole changing relay includes a main coil 2 inserted in the loopextending to the sub- Speciflcation of Letters Patent.

Patented se t. 20, 1921.

Application filed September 8, 1919. Serial No. 322,268.

' scribers oflice and an auxiliary coil 3 controlled by a receivingrelay RR in such a manner as to prevent the armature of the relay PRfrom opening the sending circuit TC in response to received signals. Therelay RR is of course controlled by the differentlal receiving relay DR.The relay RR is arranged to open and close the loo extending tothesubscribers ofiice, whic loop contains a key K and a relay 4 foroperating a sounder S at the subscribers office. At the main terminalstation a V sending key K is provided for use by the operator atsuchstation, and a sounder S 1s also provided at said station, thesounder 7 being controlled by the armature of the pole changing relayPR.

Further details of the apparatus may now be understood from theoperation which is as follows:

Signals may be transmitted either by operating the key K at thesubscribers oflice,

or by operating the key K at the main termlnal stat on. When thesubscribers loop 1s opened in response to either of these operat1ons,-the coil 2 of the pole changin relay is cle'e'nergized. Since the relayR is normally energized by current applied through the resistance 5, thecoil 3 of the pole changin relay PR is normally shortcircuited by t heground connection over the contact 6 of the relay RR consequently theopening of the subscribers loop causes the armature of thepolechangingrelay PR 'to fall off andopen the transmitting circuit TC, at the sametime actuating the sounder S The sounder S at the subscribers'ofiice isoperated-by the opening of the subscribers loop. In the normal conditionof the cir cuit, alternating current ener is transmitted through thegenerator from the circuit TC to the midpoints of the windings of thedifferential relay DR. This energy. divides between the artificial lineMN and v the transformer 1', withoutaflecting the re- 100 lay DR. Fromthe transformer 1 the alternating current energy is transmitted. throughthe tuned branch TB and over the main line ML to the distant station.The interruption .of current from the generator .105 G by the opening ofthe circuit TC, just described, actuates the receiving apparatus at thedistant station. v

The operation of the receiving apparatus at the distant statlon, which isimilar to110 that illustrated in Fig. 1, may be understood from adescription of the operation taking place at the station of Fig. 1, inresponse to signals received from the. distant station. Normallalternating current is then received rom the distant station .over themain line ML, said alternating current being selected by the tunedbranch TB and transmitted through the transformer 1 to the circuit CC.This energy flows seriall through the four windings of the relay Dthereby holding its armature to the left, as shown in thereforedeenergized and by opening con the drawing. As soon a this receivedalternating current energy is interrupted by the actuation of a key atthe distant station, the

armature of the relay DR is drawn to the right by a spring and the relayBB is shortcircuited by the ground connection over the make contact ofthe relay DR. Relay BB is tact 6 removes the short-circuit from aboutcoil 3 of the pole changing relay, so that said relay is energized tohold up the armature of the pole changing relay. At the same time thecontact 7 of relay RR is opened,

thereby opening the subscribers loop to actuate the sounder S at thelocal subscribers' office. This also results in opening the circuit ofthe coil 2 of the pole changing 7 relay PR, but since, as justdescribed, the

' signal back to the sending station.

coil 3 is at the same time energized, the pole changing relay does notrespond to the received signal to actuate the transmitting circuit TCand cannot transmit the sarrfie e sounder S does not res 0nd to receivedsignals, but is merely for t e purpose of checking transmitted signals.v

t will be obvious that the general principles herein disclosed may beembodied in ceiving relay, a pole changing relay responsive to said key,for controlling said carrier currents, and means to prevent theactuation of said. pole changing relay by said receiving relay, inresponse to received signals.

2. In a signaling system, a transmission line, means to signal over saidline by carrier currents comprising a differential receiving relay, asource of carrier current signaling energy so arranged that energy maybe transmitted to the line, without afiecting said difl'erentialreceiving relay, a normally closed subscribers loop, a sending keytherein, and a sounder associated with said loop, means whereby saiddifl'erential .receiving relay, in response to received signals, mayopen said loop to actuate said sounder, a pole changing relay associatedwith said loop in such a manner as to be responsive to said sendingkey,-said pole changing relay operating to control the transmission ofcarrier current energy from said carrier source to said transmissionline, and means to prevent the actuation of said pole changin relay whenthe subscribers loop is opened y said receiving relay to actuate thesounder associated with said loop.

'3. In a ignaling system, a transmission line, means to signal over saidline by carrier currents comprising a differential receiving relay, asource-ofl carrier current signalmg energy so arranged that energy maybe transmitted to the line without afiecting said difi'erentialreceiving relay, a normally closed subscribers loop, a sending keytherein and a sounder associated with said loop, means whereby saiddifl'erential receiving relay in response to received signals may opensaid loop to actuate said sounder, a pole changing relay having one coilin said subscribers' loop, whereby said pole changing rela in responseto the actuation of said sen ing key may control the transmission ofcarrier current energy from said carrier source to said transmissionline, and a locking coil for said pole changing relay, having itscircuit so arranged that said relay is energized under the control ofthe difierential receiving relay when said differential receiving relayopens the subscribers loop to actuate the sounder associated therewith.

In testimony whereof, I have signed my name to this specification this5th day of September, 1919.

- RALZEMOND D. PARKER.

